Introduction:
Identification of human remains is of paramount importance in medico-legal investigations. Its exigency arises in natural mass disasters such as earthquakes, tsunamis, landslides, flood, etc., and in man-made disasters such as terrorist attacks, bomb blasts, mass murders, etc., and also in cases when the body is highly decomposed or dismembered to deliberately conceal the identity of the individual [1,2]. In such cases, it is not very unusual to find dismembered human remains or peripheral body parts of the individual. Establishing biological profile of the individual is required for personal identification in such forensic investigations. To create a reliable biological profile, sex allocation proves to be a fundamental task that would further aid to inform other quantitative estimations such as age, ancestry and stature [3,4]. Sex determination is approximately 97 percent accurate when the whole skeleton is available where the pelvis contributes 95 percent of accuracy and skull contributes 92 percent of accuracy. However, sex determination gets burdened when only peripheral body parts such as hand and foot are available [5]. Fortunately, literature is occupied with studies that have weighed up the determination of sex from hand dimensions and have finally documented that sex can be determined with a high degree of expected accuracy through the analysis of anthropometric measurements of the hand [5,6-18]
Regional studies regarding such issue are of utmost importance especially in countries with enormous amounts of genetic and ethnic diversity like India [19,20]. India is composed of various heterogeneous population groups that differ in wide range of morphological and morphometric features [21]. Such variations are well acknowledged in anthropological research and are required to be assessed separately for each group. Studies have confirmed the influence of race and ethnicity on body dimensions [22,23]. However, such studies are non-existent among one of the largest indigenous populations of eastern India i.e., the Rajbanshi. Taking that fact into account, the present study has attempted to determine sexual dimorphism in the hand length and hand breadth of the aforementioned population group. Moreover, the study has derived models for determining sex using these parameters.
Materials And Methods
Nature of area and sample under study
The present cross-sectional study was based on unrelated adult individuals belonging to Rajbanshi population of West Bengal. The term “unrelated individuals” designates that consanguine relatives of the subjects such as brother-brother, sister-sister, mother-son, mother-daughter, father-son and father-daughter were not included in the study. The nature of Rajbanshi population has been discussed by Sinha et al. [24]. Adult individuals in the age group 20-60 years were chosen to be imperative for studying hand dimensions as maximum growth of hand is reached in this age group [14]. Additionally, this would ensure that the bones were mature and were not undergoing any development which could otherwise impact the accuracy of the models. The study was conducted among 400 subjects (200 males; 200 females) belonging to the aforementioned populations. The age of the individuals was recorded and verified from the age certificates (e.g., birth certificates) and other age-related proofs (e.g., voter identification cards) issued by the competent authorities. The individuals were identified as Rajbanshis by observing their physical features, cultural features and by recording their surnames. These were subsequently verified from the official records of the Gram Panchayat (local village level governing authority). All the individuals were the residents of Rajbanshi-inhabited villages named ‘Rangapani’, ‘Chotopathu’ and ‘Barapathu’ located in Jalash Nijamtara Gram Panchayat, under Phansidewa Block, Police station Phansidewa, District Darjeeling, West Bengal, India. The nearest motorable road is the Siliguri-Phansidewa highway and nearest railway station is Rangapani. The village is situated at a distance of approximately 25 kms southwest of Siliguri sub-division town of Darjeeling. Prior to data collection, necessary consent as well as permission was obtained from the respective Gram Panchayat and the subjects. The present study was conducted in accordance with the ethical standards of human experiments as laid down in the Helsinki Declaration of 2000 [25].
Anthropometric measurements recorded
Care was taken to obtain measurements only from right-handed individuals in order to ward off the genetic influence of handedness on data standards [26,27]. Measurements of hand dimensions of the subjects were retrieved by asking them to place their hands on a flat surface with palm facing upwards, fingers extended and close to each other. The idea of placing palm upwards and not downwards is solely due to ease of locating the various creases that serve as points. Care was taken to observe that there was no abduction or adduction at the wrist joint. A sliding calliper (Vernier calliper) was employed to determine the measurements of hand length (HL) and hand breadth (HB) of both sides. HL is measured from the mid-point of distal transverse crease of wrist (extending from ulnar to radial side) to the most anterior projection of the skin of the middle finger (e.g., inter stylion line) [28]. HB is measured as a distance between the radial side of the second metacarpophalangeal joint (e.g., metacarpal radiale) and the ulnar side of the fifth metacarpophalangeal joint (e.g., metacarpal ulnale) [28]. All the measurements were recorded to the nearest millimetre. Consequently, four measurements viz. left hand length (LHL), left hand breadth (LHB), right hand length (RHL) and right hand breadth (RHB) were recorded. Technical Error of Measurement (TEM) was calculated on 50 randomly selected individuals and the errors were found to be within reference values [29]. Hence, the anthropometric measurements recorded were considered to be reliable and reproducible and the TEM values were not incorporated for further statistical consideration.
Statistical analysis
The data was compiled on a Microsoft Excel datasheet (MS Excel 2013) and was later statistically analyzed with the aid of statistical software named Statistical Package for Social Sciences (SPSS version 23.0, SPSS Inc., Chicago, IL). Descriptive statistics including mean, standard deviation (SD) and range were calculated (and displayed in centimetres). One-way analysis of variance (ANOVA) based on the general linear model was evaluated to compare sex differences in HL and HB of both hands. Two-way ANOVA using general linear model was also evaluated to control the influence of age-sexes on HL and HB (left and right). The bilateral differences were also evaluated between measurements in right and left hands using ANOVA. The binary logistic regression (BLR) was performed to derive the predicting models for estimation of sex from LHL; RHL; LHB; RHB; HL and HB from individual side. Sectioning point or cut-off point in BLR was taken as 0.5. In BLR estimation of sex, the scores found more than 0.5 for the derived value were classified as females whereas scores found less than 0.5 were classified as males. The correct sex estimation accuracies were calculated in the BLR analysis. Prediction of sex is in the form of logit (p) where p=probability of being male. Logit (p) could be transformed to p by the following equation:
p=1/[1+e-logit(p)]
Results
The descriptive statistics of left- and right-hand dimensions (LHL, RHL, LHB, RHB) of male and female individuals are presented in Table 1. It is evident from Table 1 that the Rajbanshi male individuals (age range: 20 years to 60 years) exhibited mean LHL of 16.24±0.57 cm, mean LHB of 6.46±0.63cm, RHL of 16.27±0.58 cm and RHB of 6.52±0.63 cm. The mean RHL and RHB were higher than that of the LHL (16.27 cm vs. 16.24 cm) and LHB (6.52 cm vs. 6.46 cm) in male Rajbanshi individuals respectively. On the other hand, the Rajbanshi female individuals (age range: 20 years to 60 years) exhibited a mean LHL of 16.09±0.53 cm, mean LHB of 6.39±0.47 cm, RHL of 16.14±0.55 cm and RHB of 6.43±0.48 cm. The mean RHL and RHB were higher than that of the LHL (16.14 cm vs. 16.09 cm) and LHB (6.43 cm vs. 6.39 cm) in female Rajbanshi individuals respectively. It can also be seen that males possess higher mean values of LHL (16.24±0.57 cm vs. 16.09±0.53 cm), RHL (16.27±0.58 cm vs. 16.14±0.55 cm), LHB (6.46±0.63cm vs. 6.39±0.47 cm) and RHB (6.52±0.63 cm vs. 6.43±0.48 cm) compared to females. One-way ANOVA showed that there exist statistically significant sex differences in mean LHL (F-value= 6.826), RHL (F-value= 5.146) (p<0.05) but statistically insignificant differences in mean LHB (F-value= 1.937) and RHB (F-value= 2.524) (p> 0.05) (Table 1). Two-way ANOVA depicted statistically insignificant influence of sex-ages on the recorded variables (p> 0.05) (Table 1).
| Table 1: Descriptive statistics of the recorded variables |
Dimensions (cm) |
Male (N=200) |
Female (N=200) |
Mean differences in hand dimensions using ANOVA |
Range |
Mean±SD |
Range |
Mean±SD |
One-way ANOVA (F-value) |
d.f. |
Two-way ANOVA (F-value) |
d.f. |
LHL |
14.90-17.40 |
16.24±0.57 |
14.10-17.30 |
16.09±0.53 |
6.826* |
1,399 |
0.501# |
36 |
RHL |
14.80-17.50 |
16.27±0.58 |
14.10-17.20 |
16.14±0.55 |
5.146* |
1,399 |
0.468# |
36 |
LHB |
4.90-7.80 |
6.46±0.63 |
5.20-7.90 |
6.39±0.47 |
1.937# |
1,399 |
0.864# |
36 |
RHB |
4.90-7.70 |
6.52±0.63 |
5.10-7.90 |
6.43±0.48 |
2.524# |
1,399 |
0.924# |
36 |
| *p<0.05, #p>0.05 |
The bilateral difference in HL and HB among male and female Rajbanshi individuals was evaluated using ANOVA and the result of the statistical analysis is displayed in Table 2. The bilateral difference in HL and HB were found to be statistically significant in both male and female Rajbanshi individuals (p< 0.05). When HL was taken into consideration, the F-values were found to be 14.35 (d.f., 199; p<0.05) and 47.28 (d.f., 199; p<0.05) among male and female respectively. Besides, statistically significant ANOVA values (p<0.05) were also obtained for HB among the Rajbanshi male (F=38.78; d.f., 199; p<0.05) and female (36.43; d.f., 199; p<0.05) individuals. It is, therefore, evident from the statistical results that the bilateral difference in the HL and HB were influenced by the sex related effect among the subjects. Figure 1 demonstrates sex-wise frequency distribution of the recorded sample which clearly reveals sexual dimorphism for LHL, RHL, LHB and RHB.
| Table 2: Bilateral differences in hand dimensions |
|
Male |
Female |
F-value |
df |
p |
F-value |
df |
p |
HL |
14.35 |
199 |
0.000 |
47.28 |
199 |
0.000 |
HB |
38.78 |
199 |
0.000 |
36.43 |
199 |
0.000 |
Predicting models derived for determination of sex from LHL, RHL, LHB, RHB, both HL and HB from individual side using BLR analysis are shown in Table 3. The predicting models were found to be significant in hand lengths only (LHL and RHL) (p<0.01) but not in case of hand breadth (LHB and RHB) (p>0.05). The predicting models were found to be highly significant while considering hand dimensions from individual side (p<0.001).
| Table 3: Binary logistic Regression analysis for estimation of sex from recorded hand dimensions |
Measurements (cm) |
Regression Model |
Wald |
p-value |
P.A. (males) |
P.A. (females) |
P.A. (combinedly) |
LHL |
8.820 -0.548(LHL) |
8.214 |
0.004 |
78.0% |
72.5% |
75.25% |
RHL |
9.200-0.569(RHL) |
8.120 |
0.004 |
73.0% |
81.0% |
77.0% |
LHB |
1.822-0.398(LHB) |
2.839 |
0.092 |
56.0% |
58.0% |
57.0% |
RHB |
1.792-0.269(RHB) |
0.963 |
0.326 |
60.0% |
46.5% |
53.25% |
LHL, LHB |
9.489-0.937(LHL)+0.881(LHB) |
LHL:15.642; LHB:11.340 |
0.001 |
78.0% |
74.5% |
76.25% |
RHL, RHB |
9.744-0.865 (RHL)+0.661(RHB) |
RHL: 13.149; RHB: 6.764 |
0.001 |
69.5% |
70.5% |
70.0% |
| P.A.= Predictive accuracy |
Moreover, the BLR analysis revealed different predictive accuracies for each predicting model. For example, model involving LHL accurately determined 78.0% males, 72.5% females and 75.25% combinedly. RHL had accurately determined 73.0% males, 81.0% females and 77.0% combinedly. LHB had determined 56.0% males, 58.0% females and 57.0% both accurately. RHB had determined 60.0% males, 46.5% females and 53.25% both sexes accurately. Regression models using hand dimensions from each side have been proposed that can classify sex with an accuracy of (LHL and LHB= 78.0%; RHL and RHB= 69.5%), (LHL and LHB= 74.5%; RHL and RHB= 70.5%) and (LHL and LHB= 76.25%; RHL and RHB= 70.0%) for males, females and both sexes respectively.
Discussion
Anthropometric technique is single, most portable, universally applicable, inexpensive and non-invasive technique that is widely used by anthropologists and adopted by medical scientists to estimate body size and proportions for the purpose of identification and it has a prime role to play in the identification of human materials in the field of forensic anthropology and medico-legal issues [3, 30-33]. Owing to such reasons, anthropometry has also been known as Bertillon system of identification [34,35]. With the advancement of modern technology such as determination of sex with DNA analysis has disentangled forensic investigation to a greater extent. Nevertheless, anthropometry could act as a better technique in sex determination compared to DNA analysis owing to higher costs and time consumption as required by the latter method [36]. Numerous studies have been undertaken in India to determine sex from hand dimensions [11,12,14,18], but the number of studies carried out so far is negligible as India being a homeland to many ethnic and indigenous populations which definitely calls for regional studies in such aspects [37,38]. However, there is dearth of studies regarding such aspects in North Bengal (northern part of state of West Bengal, India) expect few notable studies [39-41]. Using anthropometric measurements, there exist different methods that have been employed to determine sex of the subjects such as sectioning point, discriminant function analysis, multiplication factor method and regression analyses. However, regression models have always proved to yield the maximum accuracy in sex differentiation [18,39,42].
The mean values of LHL, LHB, RHL and RHB in the present study were found to be lesser than those reported in some previous studies [7,18,33,43,44]. This could be elucidated on account of racial and/or population variation. The present study found that the male hands were significantly larger compared to the female counterparts (p<0.05) which consequently depicts sexual dimorphism with respect to HL. On the basis of HB, male hands were found to be broader than the female hands, though statistically insignificant (p>0.05). The morphometric parameters of the hand in the present study thus exhibited sexual dimorphism which is in accordance to the previous studies [11,18,33,45,46,47]. However, the sex differences were found to be statistically significant in LHL and RHL but statistically insignificant in LHB and RHB. The findings were in conformity with previous studies conducted on the hand dimensions in different ethnic communities [46-48]. The distribution of hand dimensions showed the extent and range of overlapping in male and female values for HL and HB on right and left side among the Rajbanshi individuals (Figure 1).
The predictive models are best applicable to those populations from which the data have been collected due to inherent variations in these dimensions which may be attributed to biological and environmental factors [18,46,48,49]. The present study has relied on regression methods and has found that hand length has better ability in predicting sex of the subjects. Moreover, as depicted from Table 3, hand length (Wald=8.214 for LHL and 8.120 for RHL) has greater association with sex compared to hand breadth (Wald= 2.839 for LHB and 0.963 for RHB). This finding contradicts with the findings of Kanchan and Rastogi [7] and Dey and Kapoor [14], where they have claimed hand breadth to be better predictor compared to hand length.
The findings of this study have to be seen in the light of some limitations. Since the study was conducted on live adult populations, the findings of the present study should not be applied to non-adult individuals (which mainly comprises of children, adolescents and elderly populations). On top of that, it would be imprecise to employ the result of the present study on some desiccated, decomposed and bloated bodies. The measurements of the recorded variables showed significant bilateral differences that may influence the standards and other findings of the present study. As a result, the findings which have been developed from one side are suggested not to be applied to the other side due to partial variations. However, the present study would be a valuable adjunct to other forensic identification methods. In the absence of other main body parts, hand dimensions could act as a preliminary identification.
Conclusion
It is justifiable to bring up that the present study is a pioneering study among Rajbanshi of North Bengal. The study has been successful in estimating predictive sex models from hand dimensions (LHL, RHL, LHB and RHB). Nevertheless, the accuracy in sex prediction models in forensic anthropology primarily relies upon the variations inherent in the data upon which they are built. It is hopeful that the regression models could be used to determine the (approximate) sex of an individual from the hand dimensions. The study may be successfully used for determination of sex by law enforcement agencies and forensic experts to solve different medico-legal cases.
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